In motor vehicles having tire pneumatic pressure control systems, as are disclosed in general terms by DE 40 29 311, A1, for example, the pneumatic pressure of vehicle pneumatic tires is controlled while underway by either delivering air to the tires or discharging air from these, so as to be able to influence the ride and handling of the vehicle. In this context, such systems either function autonomously or respond to the individual wishes of the driver, who via the pneumatic pressure of the tires, for example, can set the vehicle to a more sporting or a more comfortable driving mode. Such systems are also used in emergency running, that is to say in the event of damage to the tire leading to pressure losses, in order to compensate, at least temporarily, for such pressure losses.
For this purpose the air or another suitable medium, for example an inert gas, must be led from a pressure source through a rotor or stator element and delivered to the tire via a tire valve. In many cases the rotor or stator component is formed by the roller bearing of the wheel axle or of the wheel bearing. Such roller bearings with an air channel are disclosed, for example, by DE 103 23 449 A1, DE 103 24 410 A1 and U.S. Pat. No. 4,844,138.
In the technical solutions so far presented, sealing the intermediate chamber inside the roller bearing presents the greatest problems, which naturally applies to all rotor and stator systems, through which a hydraulic medium is to be led without losses. To improve the sealing, DE 103 24 410 A1 proposes an intermediate element, which is arranged in a divided bearing inner race, this rotating intermediate element possibly having air vanes. The intermediate chamber is sealed by means of two axially spaced and radially extending sealing elements, the sealing lips of which bear against the inner race. DE 103 23 449 A1 describes a similar solution having a one-piece inner race.
In U.S. Pat. No. 4,844,138 the intermediate chamber, which is substantially formed by a sub-chamber of the outer race extending from the outside radially inwards, is sealed by a permanent magnet arranged in the sub-chamber of the outer race and a magnetic fluid, which tightly seals a gap between webs of the upper sub-chamber and the inner circumferential surface of the inner race.
In the known solutions, in which seals with sealing lips are used, the strong contact pressure of the seal leads, under the pressure exerted, to a high moment of friction, which leads to a large power loss and hence to pronounced heating of the roller bearing. This can adversely affect the efficiency of the seal and the service life of the seal and of the roller bearing.